IES-VE User Forum

Hey all,
I am having serious difficulty trying to compare the day lighting levels with different glazing constructions in FlucsDL as part of my final year dissertation .
Obviously different glazing products will have different visible light transmittance, but when I change the transmittance of the external glazing in FlucsDL and calculate the illuminance levels, the results are the same even if I change the transmittance to 0%!!
Any help would be appreciated.
Thanks,
Jody

OK - prepare yourself for a ridiculous explanation...

You need to set the transmittance to zero in FLucsDL for it to grab the value set in CDB.



<On reflection I've decided to remove my cutting remarks here - no need for my rudeness apologies. Zap.>

To be honest Zap, it doesn't really surprise me!
I've been using it for a couple of months for my dissertation and its a familiar complaint. The manuals are absolutely no help either; if it wasn't for you guys on the forum, I'd be in a complete mess. I'll give it a try in the morning.
Keep up the good work,
Jody

Still no joy, still getting same results .
Looks like manual calculations will have to be done...

Hi,

Zap was right I'm afraid.

The trick here is to either use the VLT value s defined in your Construction and edit it there OR set it to 0 in the Constructions and then edit it Flucs Surface properties.

If you are doing this then possible reasons it' snot working:

1. When you set the VLT in CDB to a value other than 0.76 then when you exit CDB a warning is displayed regarding the Visible Light Transmittance with an option to change this to 0.76. If you ok this then it resets your Construction (check your CDB again to ensure it has a zero)

2. When editing in Flucs you may not be using the Assign Surface Types dialog properly (it's like the way assign Constructions works) - choose external glazing category, then select the currently assigned (UNKNOWN by default), enter the Transmittance you want to use then click the Replace button.
If you have don it right you will see a new entry appears in the "Model surface(s) of the following type" box showing the values of Inside Reflectance, Outside Reflectance and Transmittance you specified.

This does work you just need to take care to get the method right, maybe practise a bit until you see it yourself then go back to this project.

Phil

Apologies, meant to say I got it working
Not quite sure what the problem was but I just tried it again and it worked.
Thanks for the help guys

ZapBran wrote: You need to set the transmittance to zero in FLucsDL for it to grab the value set in CDB.

PCully wrote: The trick here is to either use the VLT value s defined in your Construction and edit it there OR set it to 0 in the Constructions and then edit it Flucs Surface properties.

Seems like these are two opposite directions. I would think (perhaps incorrectly) that FlucsDL would look at the VLT value assigned as a surface property within FlucsDL first, and then refer elsewhere (CDB) if the value doesn't fall within some expected threshold (i.e. NOT 0). As a regular workflow, it would make sense to specify all window properties within the CDB, and refer Flucs to there by specifying zero within Flucs.

The way Phil describes it, FlucsDL will FIRST refer to CDB and only look to the value specified within Flucs if the CDB value is zero.

Anybody mind clarifying?

I'm pretty confident in what I said but it's easy enough to check. A good exercise for you all perhaps to see how this fits together and impact of choosing extreme transmittances?

I know this sounds like a bit of a cop out and it is as I don't have time to work back through my example but this is something that is really easy to check and I'd encourage any user of VE To experiment in this way when you are questioning how something works.

Phil

PPPS (Phil's Petty PostScript) I'd be more inclined to trust me when I make a statement as I work for IES and I'm backed up by the Support Knowledge Base http://www.iesve.com/support/knowledgeb ... height=90%

Im finding the reflectance are not making any difference to my results ether. I have set the patitions from Blackboard to White gloss tile and get the same ADLF?

Is is the same principle for Radiance?